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Old 09-18-2016, 10:54 AM   #1
tehnation
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Default 8k rpm?

I'm a 05 legacy gt guy(2.5l). I currently have my motor pulled, and was designing a build for 8k rpm with about 400-500 awhp.

http://legacygt.com/forums/showthrea...ld-250013.html

My build thread.

I decided to go with brian crower stage 2 cams and springs, along with manley turbo tuff extreme duty pistons. I'm still contemplating whether to get some rods or not. I would prefer to just get some arp rod bolts and reuse my stock rods. From what I read the rods can handle it but the weakest point are the stock rod bolts. Do I really need rods?

Any thoughts or some knowledge from anyone who went this route would be appreciated.
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Old 09-18-2016, 01:15 PM   #2
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For anything above 450whp, I would suggest Manley H-tuffs which are cheap and have a ceiling up to if not above 650whp

I mean you are doing everything with the heads and pistons...and yet you stay stock with rods?
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Old 09-18-2016, 02:17 PM   #3
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Quote:
Originally Posted by user1029 View Post
For anything above 450whp, I would suggest Manley H-tuffs which are cheap and have a ceiling up to if not above 650whp

I mean you are doing everything with the heads and pistons...and yet you stay stock with rods?
I'll second user. Stock rod and rod bolts are fine less than 400 whp and 7500 rpm. It looks like your goals exceed that, so for ~$350 get some H-Tuffs with ARP 2000 bolts and you'll be nice and overbuilt. Not saying there is a certainty of the stock rods and bolts failing at those levels, but I wouldn't want to window a block because I cheaped out on a $350 set of rods.
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Old 09-18-2016, 08:04 PM   #4
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yea... looks like it's the most logical decision, rod bolts alone are 80 bucks, rods are 350 with the bolts, so for the extra 270, might as well play it safe at that point, the cost vs the value of the total investment makes it a must.
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Old 09-18-2016, 09:03 PM   #5
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Spend the little more and get the H-Tuffs. They are about <500$ Look in the privates and might find new in box for a good price.

Also if you went with stock rods/ARP rod bolts you'd have to get the rods resized which is more money. Do it once and do it right.


FYI: your motor might be able to rev to 8k but if your making under 500 there's no point to wind her out that far. Your peak HP will be before 7k and probably closer to 6,500. Nothing wrong with over building the motor so later down the road your set to go tho. If you have the money this setup would be very stout and should run for a long time.
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Old 09-18-2016, 09:17 PM   #6
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There's always a reason for more rpm range! The rpm range and hp are two completely different animals. More rpm is more speed. 400hp over 6500 rpm is way different from 400hp over 8k rpm.

The regular hbeams seem up to par. here is there info from catalog, 600+ hp at the flywheel.
Catalog link:
http://www.manleyperformance.com/dl/2016/rods.pdf

Regular 4340 forged hbeams, manley 14024-4
-Manufactured from 4340 forgings
-Heat treated, stress relieved, shot peened and 100% individually magnafluxed
-Weight matched sets + 1.5 grams
-Cap fasteners are 3/8" ARP 2000
-Flywheel horsepower range for these rods in a 4 cylinder application is 600+ and for a 6 cylinder application the range is 800+

Hplus (manley 15024-4) and hplus tuff (manley 15024R6-4) 4340 forged:
-Manufactured from 4340 forgings
-Heat treated, stress relieved, shot peened and 100% individually magnafluxed
-Weight matched sets + 1.5 grams
-Cap fasteners are 3/8" ARP 2000 for the H-Tuff and 3/8" ARP Custom Age 625+ for the H-Tuff Plus
-Flywheel horsepower range for the these rods in a 4 cylinder application is 750 with the ARP 2000 bolts
and 950 with ARP 625+ bolts. In a 6 cylinder application the horsepower range is 1000 with the ARP 2000 bolts
and 1200 with the ARP 625+ bolts.

Last edited by tehnation; 09-18-2016 at 09:24 PM.
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Old 09-18-2016, 09:22 PM   #7
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[quote=Paul;44677291]

Also if you went with stock rods/ARP rod bolts you'd have to get the rods resized which is more money. Do it once and do it right.


/QUOTE]

Why would I need to resize the rods? The arp rod bolts aren't applicable for stock?

The hplus is around 380 while the hplus tuff is around 650. I'd go with the Hplus (manley 15024-4) for an extra 30 bucks, that definitely makes a lot of sense!!

Last edited by tehnation; 09-18-2016 at 10:13 PM.
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Old 09-19-2016, 08:19 AM   #8
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Quote:
Originally Posted by tehnation View Post
There's always a reason for more rpm range! The rpm range and hp are two completely different animals. More rpm is more speed. 400hp over 6500 rpm is way different from 400hp over 8k rpm.
Problem is the VE on these motors doesn't allow for peak HP at 8k. Unless you have a huge turbo/cams your peak HP will be around 6500 and not much you can do about that just nature of the beast.

If your making under 500 there will really be no reason to rev it out past 7,500


You'd have to get the rods resized since the arps with change the shape of the big end of the rod. IMO I'd still have brand new rods checked and resized if needed but very few seem to be that OCD.

And the H-tuff with the regular arps is all you need so the price difference is very small.
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Old 09-19-2016, 10:12 AM   #9
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Don't do Hbeams, they bend very easily. H-tuff is where it's at
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Old 09-19-2016, 04:52 PM   #10
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20g and stage 2 cams arent enough? BC said an 18g can get it to 7200 rpm, and a 20g can get it to 8k rpm. I have 2 18gs atm, going to get one rebuilt to a 20g.
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Old 09-19-2016, 05:24 PM   #11
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BC says they will help make more power up there but it will be very minimal unless your running gt35r or larger.

IMO unless you plan on going way bigger down the road skip the head work if your only running a 20g. If you got the money to blow what the hell go for it but don't expect huge gains or anything. The STI heads are pretty good in stock form for 400-450whp
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Old 09-19-2016, 05:26 PM   #12
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You can spin to 8K, but why? How did you land on 8K as the redline? Without headwork and properly sized cams, there's no gains by running the engine out that far. My rotating assembly is balanced to 9K and I shift at of before 7200 as there's more benefit to going to the next gear than there is to running the engine out.
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Old 09-19-2016, 07:06 PM   #13
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Its not so much about the hp, more so the shifting. More rpm gives me more gear, i can hold the gear rather than shift in a lot of situations... i simply want more range for my gears.

Here is an article that explains it better than myself.

http://rehermorrison.com/tech-talk-4...y-rpm-matters/
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Old 09-19-2016, 09:55 PM   #14
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Originally Posted by STiSomeday View Post
You can spin to 8K, but why? How did you land on 8K as the redline? Without headwork and properly sized cams, there's no gains by running the engine out that far. My rotating assembly is balanced to 9K and I shift at of before 7200 as there's more benefit to going to the next gear than there is to running the engine out.
Did you read the thread? He plans on getting head work and cams. While that will shift the power band to the right it will be very minimal on smaller turbos like a 20g
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Old 09-19-2016, 10:15 PM   #15
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So bigger turbo ..... lol

http://www.atpturbo.com/mm5/merchant...egory_Code=SUB

That's the cherry on top. I guess i'll hold off on rebuilding one of my 18gs, sell it, and save for a big boy turbo. ****in turbo is the cost of all the parts needed for head and block and then some.... once it starts it never ends!
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Old 09-20-2016, 08:08 AM   #16
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The gtx3576r is a great turbo but I would suggest getting it in rotated form and not with a bolt on Subaru housing
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Old 09-20-2016, 10:52 AM   #17
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The gtx3576r is a great turbo but I would suggest getting it in rotated form and not with a bolt on Subaru housing
Other option is the Killer B Spoolinator kit. Allows retention of stock TMIC and stock-like appearance, but overcomes the lack of proper turbine housing options. Still a fairly expensive endeavor, but not as bad as fully rotated.
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Old 09-20-2016, 11:29 AM   #18
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^true

Although unless your reusing parts it's really not cheaper compared to the lower cost rotated kits.
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Old 09-20-2016, 03:09 PM   #19
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deleted post, missed the one where you posted the larger turbo selection. I agree with Paul, go rotated so you can pair it with a proper turbine housing. Because you are chasing high RPM you need as much efficiency as you can get.
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Old 09-20-2016, 04:44 PM   #20
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Quote:
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Did you read the thread? He plans on getting head work and cams. While that will shift the power band to the right it will be very minimal on smaller turbos like a 20g
I did, but the OP was talking about using a 20g turbo. Peak power will be where it is, probably a lot earlier than 8K with a 20g. Aiming for a seemingly arbitrary redline doesn't make sense to me. Just spin the motor out to wherever the benefit of holding the gear out is outweighed by the benefit of shifting to the next gear.

Now that he's considering bigger turbos, it makes more sense to want to be able to hold the gears out longer.
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Old 09-20-2016, 08:55 PM   #21
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I've been debating this as well while thinking about my backup block, and I always come back to the thought that having the headroom wouldn't hurt, and overbuilding is always better.

Raising the RPM isn't so much about the shortblock though, much more-so the heads. Heavy duty springs most of all to avoid float from what I've read.
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Old 09-20-2016, 10:05 PM   #22
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I've been debating this as well while thinking about my backup block, and I always come back to the thought that having the headroom wouldn't hurt, and overbuilding is always better.

Raising the RPM isn't so much about the shortblock though, much more-so the heads. Heavy duty springs most of all to avoid float from what I've read.
Bottom end shouldn't be neglected either. You'll want to balance the rotating assembly, ensure your oil clearances are good for high rpm applications and make sure your oil pump is sufficient enough to flow well that far up in the rev range. You also need to make sure your rod bolts can handle the stretch and your quench isn't too tight.
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Old 09-21-2016, 03:46 PM   #23
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^very true!!

And honestly 8k isn't anything crazy my stock JDM motor saw that about every time I drove it. Lol

A ej257 I'd rev stock to 7,500 without worry but id want springs for 8k just for piece of mind

Edit: While over building is a good idea when/if you have the money but if you don't I wouldn't. I've seen too many people go over board on a build but then go broke 90% of the way cause they didn't think about all the little stuff that adds up. Or they don't keep up with maintenance or spend all this money then run crap tires.
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Old 09-21-2016, 04:28 PM   #24
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gotta love how japan always keeps the best stuff for themselves.

Im taking it slow and steady, I have another car so it's not to bad.

Basically I will see where the 18g gets me and take it from there. Judging from that data, i will be able to see realistically what I need to get me where I want to be.

I've decided on the regular htuffs, 15024-4, it's a nice middle ground, 750 hp with the arp2000 bolts, that's plenty of headroom considering i'm aiming for 400-500whp.

To spend all this money and not balance the rotating assembly .... that's just crazy lol!

I was going to go with stock oil clearances, and tightest fit ptw. The rod bolts will be pre stretched for sure.

I bought the 11mm sti oil pump. Should be enough.

Last edited by tehnation; 09-21-2016 at 08:10 PM.
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Old 09-21-2016, 07:06 PM   #25
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Quote:
Originally Posted by Paul View Post
FYI: your motor might be able to rev to 8k but if your making under 500 there's no point to wind her out that far. Your peak HP will be before 7k and probably closer to 6,500. Nothing wrong with over building the motor so later down the road your set to go tho. If you have the money this setup would be very stout and should run for a long time.
Here's a case in point. My 20g-xtr build has all the forged goodies and exhaust cams. I'm sure it would run to 8k but my tuner told me there would be not much point, as shifting above 7200 puts me well above the max tq rpm as well.

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